Along with the development of wireless communication systems, more services and more service data are required. To meet the demands, a broadband wireless mobile communication system has emerged. However, due to limited frequency resources, the wireless mobile communication system has limited frequency bands. Accordingly, there exists a need for increasing frequency bands available for providing broadband services.
FIG. 1 illustrates a single-frequency band supporting structure and a two-frequency band supporting structure in a conventional wireless mobile communication system.
In a wireless mobile communication system, especially based on Institute of Electrical and Electronics Engineers (IEEE) 802.16, a base station (BS) manages one or more frequency assignments and provides a service to a mobile station (MS) in at least one of the frequency assignments.
Referring to FIG. 1, a mobile station (MS) 100 can switch from a first frequency assignment (FA) 120 (FA1) to a second frequency assignment (FA) 140 (FA2). If the MS 100 is limited to only one FA or different base stations manage the two FAs 120 and 140, the MS 100 receives a service in FA2 by an inter-FA handover.
If an MS 150 can operate in two or more FAs or the same base station (BS) manages two FAs 160 and 180 (FA1 and FA2), the MS 150 can receive a service in the FAs 160 and 180. In this manner, signal transmission and reception between an MS and a BS in multiple FAs is favorable for high-speed, large-data transmission and reception. However, a procedure for using multiple FAs between the MS and the BS is yet to be specified. Also, a technique for enabling the MS to fast switch from a current FA to a new FA or from a serving BS to another BS is to be developed.